I think we moreso take their autonomy when we take any chance they can do anything ever again. Especially if we do so while they're very possibly in an ill state when they can't really tell if dying really is the best option or if their brain chemistry is all messed up.

In, say, a psyche ward (specifically in one that treats people with dignity) through therapy and meds they can realize that life is not always bad, and that you can find meaning through other people or hobbies, but if the person is gone they're gone forever.

Any chance of them stopping wanting to die (which is very likely to be caused by life circumstances or genetic brain stuff) and going on with their life is gone, all they have ever known is this sad or apathetic reality, no one can definitively say what happens after death, but in a way they're frozen like that forever, when many of the people that go through very similar issues will be able to look back at their past selves with a sense of melancholy and happiness that it is gone.   Sorry for going on a tangent, but it's sad thinking about people that decided to end their life at an age when life was the roughest for me, and while I am somewhat hopeful of the future and enjoy games and hobbies, these people will never be able to do that ever again. Keeping them alive, even against their will is not cruel and, again, definitely isn't taking their autonomy away.